Objective: To determine whether psyllium fiber (in the form of Metamucil) interferes with absorption of calcium ingested at the same meal.
Design: Three-way, randomized, cross-over study in 15 healthy postmenopausal women, with calcium-fortified orange juice as the calcium source in all three meals. The test load of calcium was 219 mg (approximately 5.5 mmol). One test meal contained Metamucil, providing 3.4 g psyllium fiber; one had an equivalent amount of neutral cellulose; the third had no added fiber.
Methods: The calcium-fortified orange juice was extrinsically labeled with 45Ca; calcium absorption fraction was calculated from the specific radioactivity of serum calcium at 5 hours after tracer ingestion.
Results: Fractional absorption of calcium from orange juice without added fiber averaged 0.341 +/- 0.059; in the presence of psyllium fiber, 0.317 +/- 0.067; and in the presence of neutral fiber, 0.354 +/- 0.083. While the absorption with cellulose was slightly higher than in the absence of fiber, and the absorption with psyllium was slightly lower, neither difference was statistically significant. However, the difference between added psyllium and cellulose was statistically significant (P < .05).
Conclusion: Psyllium in the form of Metamucil makes little practical difference to availability of co-ingested calcium when ingested at typical therapeutic doses.